Since a wavelength tunable laser that can change its oscillation wavelength is expected to be applied to various fields, such as communication, sensing, and imaging, the wavelength tunable laser is being actively studied and developed in recent years. As such a wavelength tunable laser, a configuration that moves one of a pair of reflecting mirrors of a vertical cavity surface emitting laser (hereinafter, referred to as VCSEL) is developed. To be specific, the cavity length is varied by mechanically moving one (a movable mirror) of the pair of reflecting mirrors by micro electro mechanical systems (hereinafter, referred to as MEMS) technology and hence the oscillation wavelength of VCSEL is changed.
Also, for the movable mirror, a distributed Bragg reflector (hereinafter, referred to as DBR) may be used. NPL 1 discloses wavelength tunable VCSEL including dielectric DBR as a movable mirror.